This application relates to a gas turbine engine in which cooling air is provided from an upstream location in a compressor to cool high pressure air to be utilized as cooling air for gas turbine engine components.
Gas turbine engines are known and typically include a fan delivering air into a bypass duct as propulsion air and also into a core engine. The air in the core engine enters a compressor where it is compressed and then delivered into a combustion section. The air is mixed with fuel and ignited and products of this combustion pass downstream over turbine rotors driving them to rotate.
Historically, a fan drive turbine rotated at a single speed with the fan. However, more recently, a gear reduction has been placed between the fan drive turbine and the fan rotor. This allows the fan to increase in diameter and rotate at slower speeds, which has many beneficial effects.
Also, the fan drive turbine is able to rotate at higher speeds. Temperatures within the gas turbine engine increase with this change for several reasons. Further, the pressure downstream of the combustor also increases.
As can be appreciated, components of the gas turbine engine and, in particular, those in the turbine section see very high temperatures. It is known to provide cooling air to cool those components. However, due to the increased pressure, it becomes desirable to use highly pressurized air as the cooling air such that it is able to move into the turbine section. The most pressurized air in the gas turbine engine is downstream of a high pressure compressor and it is typically hot.
Thus, cooling for this high pressure air becomes necessary. It has been proposed to cool this high pressure air in a heat exchanger sitting in the bypass duct. However, the fan pressure ratios delivered by the increased diameter fans are dropping and, thus, may not provide efficient cooling.